1. Field of the Invention
The present invention relates to a hydraulic lift for motor vehicles and in particular relates to an improved high pressure hydraulic chain lift.
2. Description of the Prior Art
Hydraulic lifts for motor vehicles are often set underground. In their retracted state, the external members of the lift withdraw into the floor. This configuration is convenient because it is less cumbersome and consumes less space than above-ground lifts. Many underground lifts in the past were operated using low hydraulic pressure. Hydraulic lifts operated with low pressure often require a large amount of oil or other hydraulic fluids in their operation. Low pressure lift systems typically use approximately 45 gallons of hydraulic oil. In addition, prior hydraulic lifts typically included a reservoir tank of hydraulic oil buried underground along with the lift. It is often difficult to determine the existence of an oil leak from the underground tank before a large amount of oil seeps into and permeates the surrounding environment. This is especially true with low pressure lifts. Storing the tank underground also makes maintenance of the lift more difficult and cumbersome.
U.S. Pat. No. 5,148,827, issued to Howard A. Masters on Sep. 22, 1992 describes an air-oil full hydraulic reservoir tank in which a hydraulic lift cylinder raises and lowers a piston as air is forced into the reservoir tank, thereby forcing oil from the reservoir tank and into the lift cylinder.
U.S. Pat. No. 5,143,179, issued to Roland Hornstein on Sep. 1, 1992 describes a high pressure lifting platform where a relatively narrow high-pressure cylinder is coaxially positioned within an outer supporting piston. Lubrication of the friction surface between the guide bushing and the piston is automatically regulated.
U.S. Pat. No. 5,129,483, issued to Hans Nussbaum on Jul. 14, 1992 describes a lift using a cylinder-piston arrangement with a cable and deflection roller attached to a lift cylinder disposed within a piston with telescoping sleeves.
U.S. Pat. No. 5,052,520, issued to Koji Wakamiya on Oct. 1, 1991 describes an underground hydraulic lift including sliders with attachment holders in which desired attachments for directly supporting a vehicle can be detachably set.
Japanese Kokai ("laid-open") Patent No. 52-31443 issued to Tozaburo Tsujimura on Sep. 3, 1977 describes a safety device for a vehicle lift in which an eccentric cam engages a support post to prevent the carriage from accidentally dropping when the chain for lifting the carriage breaks.
U.S. Pat. No. 3,788,197, issued to Billy H. Bishop on Jan. 29, 1974 describes a protective housing for preventing corrosion from the electric current to the lift mechanism.
None of the above patent references, either alone or in combination, is seen to describe the instant invention as claimed. While these and other patents disclose underground lifts using hydraulic cylinders in conjunction with pistons, the known prior art does not disclose or suggest the use of the particular pulley and chain system of the present invention for a more efficient hydraulic lift system.